Electrostatic precipitator power connection



Nov. 9, 1965 R. S. COOPER ETAL ELECTROSTATIC PRECIPITATOR POWER CONNECTION Filed March 28, 1960 FIG. I

MAIN GAS H OUTLET Z7 3 Sheets-Sheet 1 t PURGE GAS OUTLET I I I J I GAS INLET ROY G. WINKLEPECK ROLAND S. COOPER INVENTORS Nov. 9, 1965 R. s. COOPER ETAL 3,216,180

ELECTROSTATIC PRECIPITATOR POWER CONNECTION Filed March 28, 1960 3 Sheets-Sheet 2 ROY G. WINKLEPECK ROLAND S. COOPER lNVENTORs QMW FIG. IA

0 NEY Nov. 9, 1965 R. s. COOPER ETAL 3,216,180

ELECTROSTATIC PREOIPITATOR POWER CONNECTION Filed March 28, 1960 3 Sheets-Sheet 3 DUCT MOTION d 3 B W JG W. A 6 A 5 C 2 E m w U m 3 0 O m mm EH u E m rm 3 4 E E Emu: 0 mmn 5 R F s I 5 2 5 /.w vsah lk n a 2 ll l*s 753 U 6 2222m N 753 2222 6 nV 2 3333 6 753 63 3333 753 m I IVL F 4444 8642 l H 4444 8642 5555 MW 8642 5555 U 8642 B fi 6666 8642' 6666 8642 6 FIG. 4

ROY G WINKLEPEOK ROLAND S. COOPER INVENTORS %RNEY FIG. 4A

HOODS United States Patent 3,216,189 ELECTROSTATIC PRECIPITATOR POWER CGNNECTHON Roland S. Cooper, Greenwich, Conn, and Roy G. Winklepleclr, Roslyn Heights, N.Y., assignors to Refractory &

Insulation Corporation, a corporation of Delaware Filed Mar. 28, 1960, Ser. No. 18,963 2 (Jlairns. (Cl. 55-111) The present invention relates to gas cleaning apparatus of the electrostatic precipitator type in which particles deposited on the collecting surfaces by a process of electrostatic precipitation are removed by a stream of purging fluid. The invention relates particularly to an improved arrangement for supplying power to the ionizing electrodes which results in increased efficiency of the cleaning.

In gas cleaning apparatus of the electrostatic type, dust laden gases are directed through a strong electric field between discharge electrodes and grounded collector surfaces. As the dust particles entrained in the gas stream become electrically charged, they move under the influence of the strong electric field to the grounded collector surfaces upon which they are deposited.

In order that the dust collecting apparatus may be maintained at a high operating efficiency it is of primary importance that all electrodes and collecting surfaces be periodically subjected to a cleaning action to remove the deposited particles and thereby present a substantially clean surface to the incoming dust entrained fluid. Since the operating efficiency of dust collecting apparatus is dependent to a large extent upon the efiiciency with which the deposited particles are removed from the collecting surface of the precipitator, it is an object of this invention to provide an arrangement for efiiciently removing the deposited particles from the collecting surfaces thereof, thereby preventing them from reentrainment in the clean gas stream issuing from the precipitator.

The invention is adapted for use with electrostatic precipitators of the type disclosed in the Karlsson Patent 2,582,133 or the Hodson Patent 2,887,176 wherein groups of tubular collecting surfaces and their associated ionizing electrodes are individually isolated from the remainder of the precipitator and subjected to the action of a stream of purging gas which cleans the deposited particles from the tubular collecting surfaces. The invention is particularly adaptable to a precipitator in which the charging current for the isolated electrodes is not cut off during the purging period. The invention contemplates arranging the electrical supply connections for the various groups of electrodes so as to maintain a higher average degree of cleanliness for all of the electrodes connected to a single power supply in the intervals elapsing between successive applications of the stream of purging fluid to the related collecting surfaces.

In a precipitator of the Hodson type wherein the compartments containing numbers of tubular collecting surfaces with associated electrodes are arranged in a series of parallel rows, the application of the stream of purging fluid to a compartment in any one row results in the corresponding adjacent compartments in other rows (which compartments are connected to the same power supply) being forced to wait a relatively long time before they are cleaned. The result is that the accumulations of particles on the collecting surfaces may build up to such a high point that flashovers occur or the accumulation of particles renders it difiicult to apply a desired high charging voltage to the precipitator electrodes; in other words, it restricts the input of charging current and thereby reduces precipitating efficiency. The invention contemplates re-arranging connections to the power supplies 3,215,.l8h Patented Nov. 9, 1965 to the various electrode compartments so that all of the compartments connected to a single power supply are cleaned in succession with the result that the time interval between effective cleaning of the first and last compartments of a group connected to a particular power sup ply are reduced.

FIGURE 1 is an elevational view partly broken away of an illustrative form of electrostatic precipitator to which the invention is applied; FIG. 1A is an enlarged view of fragmentary portion at the lower part of FIG. 1.

FIGURE 2 and 2A are related diagrams indicating a conventional manner of connecting power supplies for the various compartments of a rectangular electrostatic precipitator where the compartments are arranged in several adjacent rows.

FIGURES 3 and 3A are related diagrams illustrating how the present invention is applied to the connection of the power supplies for such precipitator compartments.

FIGURES 4 and 4A are diagrams illustrating the application of the invention to a precipitator in which the compartments are arranged in, or sectors of, a circle, and form a cylindrical precipitator.

In FIGURE 1 the numeral 10 designates a rectangular housing enclosing an electrostatic precipitator having collecting compartments 12 through which dust laden gases pass to a duct 14 from which the cleaned gases are vented after dust has been precipitated therefrom onto the surfaces of collecting tubes 16 in which the ionizing electrodes 18 are centrally mounted. The compartments 12 lie between a series of transverse division plates 22 which extend through the housing in a plane normal to longitudinal partitions 24. At the upper end of compartments 12 a series of converging extensions 19 thereto form continuations whose end faces combine to form a perforate arcuate surface whose ports discharge cleaned gases into outlet chamber 26. An imperforate sealing surface 27 continuing from the arcuate surface forms therewith a completely cylindrical rnember enclosing chamber 26 which directs cleaned gases axially outward through outlet duct 14.

A plurality of axially contiguous but cricumferentially displaced branch purging nozzles or ducts 3&2, b, c etc. depend from a cylindrical duct 34 and are adapted to rotate therewith about the axis of bearing supported trunnions 30. These branch ducts 36a, b, c, d are each provided at their distal ends with a sealing surface 35 arcuately formed to supplement the arcuate surface 27 of the cylindrical member. The end openings in the sealing surfaces 35 are adapted to sequentially register with the end openings in the parallel rows of compartments upon rotation of the central duct 34 and its appended ducts 36. A single branch duct 36 is provided for each row of compartments lying between longitudinal partitions 24, the angular displacement of each duct being dependent upon the number of ducts. For example, a four bank precipitator as illustrated requires'a cleaning arrangement having four branch ducts 36a, b, c, d each displaced degrees from one another. By the same token a three bank precipitator would require three branch ducts each displaced degrees while a precipitator having six banks of cleaning compartments would require a like number of branch ducts each displaced at an angle of 60 degrees from one another.

The imperforate portion 27 of the cylindrical housing provides a surface which cooperates with the ends of the branch ducts 36a etc. to seal them when they are in a confronting relationship, and only the particular branch duct in alignment with any of the several rows of compartments 12 will be open to permit the flow of purging fluid therethrough. As the duct 34 rotates about its axis and the branch ducts 36a, b, c, d are sequentially brought into alignment with the rows of collecting chamber 12,

the ducts in turn become active in the transmission of a purging fluid through the compartments in one row after another to a prescribed outlet.

Purging fluid for the cleaning device is drawn from the main gas flow by an induced draft fan (not illustrated) connected in outlet 39, the course of purging fluid flow being from the precipitator inlet through a single compartment 12 thence through the branch duct 36 in agreement therewith to the central duct 34 and axially outward through ports 32 to outlet duct 39.

In operation the central duct 34 and its appended branch ducts 36a, b, c, d are rotated slowly about their horizontal axis by an actuator such as a motor 42 acting through suitable reduction gearing 44. The device 44 may include mechanism for either continuous or intermittent drive as may be deemed appropriate for the conditions involved. As the central duct is rotated about its axis only one complete branch duct can at any time register with an extension 19 from compartments 12, all other branch ducts being sealed against the imperforate surface of the cylindrical wall 27, this being shown in FIG. 1. As each branch duct is in turn moved into registry with succeeding extensions 19 of compartments 12 a flow of purging fluid is directed therethrough to the central duct 34 where it is then channeled through outlet ports 32 to exit duct 39. As the cylinder 34 is rotated the spaced branch ducts 36b, 0, d sequentially follow duct 36a to be moved past the collecting compartments into a confronting relationship with the imperforate arcuate surface 27 of the cylindrical housing where they are in turn sealed off as the next duct is rotated into confronting relationship with the extensions 19 of compartments 12.

The physical features of the electrostatic precipitator described above correspond to the disclosure of the Hodson patent. Heretofore, as represented in FIGS. 2 and 2A, a single electric power supply has been employed in conjunction with corresponding transversely alined compartments in the several rows I to IV across the precipitator, a single power supply being connected to one or several tiers of compartments such as those bearing the designation 1. The purge stream ducts or nozzles are represented at 36a, b, c and d in FIGURE 2A in alinement with the longitudinal rows of compartments which they clean, the staggered relation in FIG. 2A corresponding to the angular separation of the purge ducts illustrated in FIG. 1.

In FIGURE 2 the power supply 5G is indicated to be connected to four transversely alined compartments bearing the numeral 1 from each of the rows I to IV. The four other compartments to the left designated by the numeral 1 are likewise connected to this power supply but illustration of the connections is omitted to avoid unnecessarily complicating the figure. At the left hand end a similar connection is shown for compartments 6 in the rows I to IV and it is to be understood that the groups of compartments designated 2, 3, 4 and 5 are likewise connected to related individual power supplies.

In accordance with the present invention, the power supplies are connected to the compartments so that each power supply serves only a group of compartments located in a single longitudinal row as indicated by the connections 60 from power supply 62 to the compartments designated by the numeral 1 in row I of FIG. 2A. The row I also comprises additional groups of compartments as those designated 2 which are shown connected at 61 to the power supply 63. Likewise groups of compartments in the other longitudinal rows II, III and IV are connected to common power supplies in cases where the compartments bear the same numerals, such as 3 or 4, this however being additionally shown only at 65 and 66 in connection with the compartments designated 7 and 8 in the row IV; to add connections for the compartments marked 3 to 6 would unnecessarily complicate the figure. As will be seen in FIG. 3A, the cleaning hoods or ducts 36a, b, c and d for the several rows I to IV move together in the direction of the longitudinal row-s so that each of the compartments in the group designated 1 is cleaned in succession by the hood 36a before the latter cleans the compartments in the group bearing the numeral 2. The purge ducts 36b, 0 and d do not come into effective operation until the preceding duct has finished with its row, as for example the duct 36a completely traverses the compartments of the groups designated 1 and 2 in the row I before the duct 36b becomes alined with the first compartment designated 31in the row II.

Thus, groups 1, 2 etc. adjacent compartments along the length of the precipitator are connected to the same power supplies. In FIGURE 3A the hoods 36 do not have cover plates and purging is accomplished without voltage suppression.

Assuming that a hood such as 36a cleans a compartment for 3.75 seconds and that the entire purge cycle takes 180 seconds for the hoods 36a, 36b, 36c and 36d to clean all the compartments, it can be shown that with the power supplies connected as shown in FIG. 2 the dirtiest compartment in any group will have been accumulating particles for 138.75 seconds at the time when the cleanest compartment of the group connected to the same power supply has just been purged. For example, when the left hand compartment IL in row IV has just been purged by the hood 36d the dirtiest compartment will be that designated 1F at the right in the row I which has been accumulating particles for 138.75 seconds. This is because with four hoods it takes three quarters of the cleaning cycle or seconds for the hood 36d to reach the compartment 1L after the hood 36a has moved away from the compartment 1F. The additional 3.75 seconds over 135 being due to the length of time that the hoods clean the first tier designated 1 before reaching the second tier. As contrasted with this, the power connections illustrated in FIG. 3 result in that when the last compartment 1L of the group 1 has just been cleaned, only 22 /2 seconds will have elapsed since the compartment 1F was cleaned by the hood 36a. Thus when the power supplies are connected as shown in FIG. 2, the difference between the cleanest and the dirtiest compartment in the group designated 1 is 138.75 seconds from cleaning of the first of the group to the cleaning of the last; whereas in FIG. 3 the interval between the cleaning of the first and last of group designated 1 is 22 /2 seconds. Inasmuch as flashovers occur in any group connected to a power supply in accordance with the state of the dirtiest compartment of the group, it will be apparent that the difference of the arrangement of FIG. 3 of only 22%. seconds of accumulation between the cleanest and the dirtiest compartment at any time is much less likely to result in flashovers than with the power connections of FIG. 2 where the difference in cleaniness between the last cleaned and the first cleaned in the group amounts to 138.75 seconds.

FIGS. 4 and 4A are in principle the same as FIGS. 1 and 1A, 3 and 3A except as applied to a rotary unit. In this case FIG. 4 perm-its the average power supply output to be based on dirt accumulation and for FIG. 4 on between 15 and seconds.

What we claim is:

1. In an electrostatic precipitator having a plurality of collecting surfaces and associated ionizing electrodes distributed among a plurality of compartments arranged in a number of separate but adjacent groups, each group consisting of a number of contiguous compartments; means for cleaning the compartments of each group in sequence and prior to the cleaning of a compartment in any other group; and means individual to each group of compartments for separately supplying an ionizing current to the electrodes of all of the compartments of each group.

2. In an electrostatic precipitator having a plurality of collecting surfaces and associated ionizing electrodes distributed among a plurality of compartments arranged in 5 6 a number of separate but adjacent groups each consist- 2,853,156 9/58 Hodson. ing of a number of contiguous compartments; means for 2,863,523 12/58 Klemperer 55117 cleaning the compartments of each group in sequence and 2,887,176 5/59 Hodson. prior to the cleaning of a compartment in any other group; 2,936,042 5/ 60 Hodson 551l1 and a common means for supplying an 10I11Z11'lg current 5 FOREIGN PATENTS to all of the compartments of a group, there being separate power supplies for each group.

References Cited by the Examiner ROBERT F. BURNETT, Primary Examiner.

UNITED STATES PATENTS 10 HERBERT L. MARTIN, WALTER BERLOWITZ, 2,582,133 1/52 Karlsson 55- 114 ARNOLD RUEGGExammm- 788,059 12/57 Great Britain. 

1. IN AN ELECTROSTATIC PRECIPITATOR HAVING A PLURALITY OF COLLECTING SURFACES AND ASSOCIATED IONIZING ELECTRODES DISTRIBUTED AMONG A PLURALITY OF COMPARTMENTS ARRANGED IN A NUMBER OF SEPARATE BUT ADJACENT GROUPS, EACH GROUP CONSISTING OF A NUMBER OF CONTIGUOUS COMPARTMENTS; MEANS FOR CLEANING THE COMPARTMENTS OF EACH GROUP IN SEQUENCE AND PRIOR TO THE CLEANING OF A COMPARTMENT IN ANY OTHER GROUP; AND MEANS INDIVIDUAL TO EACH GROUP OF COMPARTMENTS FOR SEPARATELY SUPPLY AN IONIZING CURRENT TO THE ELECTRODES OF ALL OF THE COMPARTMENTS OF EACH GROUP. 